Association between Weather-Related Factors and Cardiac Arrest of Presumed Cardiac Etiology: A Prospective Observational Study Based on Out-of-Hospital Care Data

<p><b>Objective</b>: The objective of this study was to determine the association between weather-related factors and out-of-hospital cardiac arrest (OHCA) of presumed cardiac etiology. <b>Methods</b>: This was a prospective observational study performed in a prehospital setting. Data from the Emergency Medical Service in Hamburg (Germany) and data from the local weather station were evaluated over a 5-year period. Weather data (temperature, humidity, air pressure, wind speed) were obtained every minute and matched with the associated rescue mission data. Lowess-Regression analysis was performed to assess the relationship between the above-mentioned weather-related factors and OHCA of presumed cardiac etiology. Additionally, varying measuring-ranges were defined for each weather-related factor in order to compare them with each other with regard to the probability of occurrence of OHCA. <b>Results</b>: During the observation period 1,558 OHCA with presumed cardiac etiology were registered (age: 67 ± 19 yrs; 62% male; hospital admission: 37%; survival to hospital discharge: 6.7%). Compared to moderate temperatures (5 – 25°C), probability of OHCA-occurrence increased significantly at temperatures above 25°C (p = 0.028) and below 5°C p = 0.011). Regarding air humidity, probability of OHCA-occurrence increased below a threshold-value of 75% compared to values above this cut-off (p = 0.006). Decreased probability was seen at moderate atmospheric pressure (1000 hPa – 1020 hPa), whereas increased probability was seen above 1020 hPa (p = 0.023) and below 1000 hPa (p = 0.035). Probability of OHCA-occurrence increased continuously with increasing wind speed (p < 0.001). <b>Conclusions</b>: There are associations between several weather-related factors such as temperature, humidity, air pressure, and wind speed, and occurrence of OHCA of presumed cardiac etiology. Particularly dangerous seem to be cold weather, dry air and strong wind.</p

Impact of propofol on neurotrophins.

<p>Densitometric quantifications of mRNA levels of BDNF and NT-3 in cortex and thalamus of P6 rats, analysed by qRT-PCR. Values represent mean normalised ratios of the densities of BDNF and NT-3 bands compared to the density of the control group (n = 6–7/point+SE). There was an effect of propofol treatment with a decrease of BDNF levels over time, which was significant after 6 hrs in the cortex [F(1,30) = 66.5, p<0.001]. There was also a decrease in NT-3 levels, which was significant in the cortex after 6 hrs [F(1,28) = 12.7, p = 0.004] and after 12 hrs in the thalamus [F(1,24) = 3.5, p = 0.06].</p

Impact of propofol on survival promoting proteins.

<p>Densitometric quantifications of pAKT and pERK1/2 in the cortex and thalamus of P6 rats, analysed by Western blotting. Values represent mean normalised ratios of the densities of pAKT and pERK1/2 bands compared to the density of the control group (n = 6/point+SE). There was an effect of propofol treatment in decrease of pAKT levels over time in the thalamus, which was significant after 12 hrs [F(1,28) = 5.6, p = 0.06]. Post-hoc analysis showed most pronounced decrease after 12 hrs (2-sample t-test). In the cortex there was a significant decrease of pERK1/2 levels over the time, which was significant after 6, 12 and 24 hrs [F(1,29) = 12.7, p = 0.013].</p

Impact of propofol on key proteins involved in apoptotic signalling.

<p>Densitometric quantifications of caspase-3 and AIF in cortex and thalamus of P6 rats as analysed by Western blotting. Values represent mean normalised ratios of the densities of caspase-3 and AIF bands compared to densities of the control group (n = 5–6/point+SE). There was an effect of propofol treatment on caspase-3 levels over time, which was significant after 24 hrs in the cortex [F(1,29) = 3.63, p = 0.06] and after 12 hrs in the thalamus [F(1,28) = 3.1, p = 0.09).</p

Novel object recognition on P30 and P120: At the age of 30 days, both propofol treated animals (t(7) = 7.45, ***q = 4.3×10⁻⁴) and controls (t(10) = 6.30, ***q = 3.6×10⁻⁴) spent significantly more time with the novel object indicating their ability to discriminate the novel from the old object.

<p>Propofol (t(7) = −1.44, q = 0.192) as well as control animals (t(10) = −1.92, q = 0.168) failed to do so after a 24 hrs inter-trial interval. At P120 both groups spent a random amount of time with either of the objects after 6 hrs and also after a 24 hrs interval, indicating that they were unable to remember the old object. (n_controls = 12 animals, n_propofol = 8 animals).</p